Fix the build problems in issue 22 related to FFI

[dan-at-confirm]

Issue: https://github.com/tmthecoder/dargon2/issues/22

This PR is being opened on behalf of @qui-jason.

It seems there was an upgrade to the ffi plugin that requires a minor change.

[qui-jason]

Didn't realize this branch was associated with a PR, sorry about that. FWIW I tried to make the arm64 runner work with android tests and kept running into this issue: https://github.com/actions/runner-images/issues/9472#issuecomment-1984324388 which is why there are so many commits.

Tests are passing, I'll squash some stuff.

[qui-jason]

Flutter tests pass after upgrading some of the CI toolchain, but the top level workflow is commented out at the moment.

[dan-at-confirm]

@tmthecoder how does this look to you?

[qui-jason]

I fixed the top level tests as well, but I used a deprecation override to do so. The correct solution (required for Dart 3.4) is to use isolates, I believe.